5w40 v 5w30 oil

[mrscalex]

I know this has been an oft talked about subject in the past with various schools of thought generally resulting in the view that 5w30 is better than 5w40. And people groan when it crops up again... But despite all these posts I've never seen a properly balanced view given.

What are the pros and cons for each? Is there a reason to buy 5w40 instead of 5w30? Better for an older engine maybe?

If I buy a decent make like Shell Helix Ultra does it make any difference the age all our Z3s are now?

[lightning]

I am not sure it will make any difference whether you use 5w/30 or 5w/40.

5w/30 is used in modern cars for fuel economy reasons as it's slightly thinner at operating temperature. If an engine is worn or older it may burn slightly more oil (than if 5w/40 is used)
Also 5w/40 would be better for use in ambient temperatures above 40deg....unlikely in the UK.

Personally l use 5w/40 only because BMW recommend it.

[Del]

Agree with Lightning. It's probably not that critical and I suspect 5W-30 wasn't used widely when Z3s rolled off the production line

[mrscalex]

Thanks chaps. 5w40 it is.